1. Field of the Invention:
The invention relates to apparatus for monitoring body conditions and more specifically to an electro-mechanical apparatus specifically useful for monitoring sounds related to systolic and diastolic pressure measurements as well as sounds related to the heartbeat and respiratory functions.
2. Description of the Prior Art:
During the course of a majority of surgical procedures, sterile drapes often limit the anesthetist's ability to observe the thorax and patency of the airway. For this and other reasons, anesthetists have come to rely heavily upon auditory monitoring, such as through a stethoscope sound pickup piece placed on the chest wall, precordial, or placed in the esophagus, esophageal, directly behind the trachea or "windpipe". Besides indicating heart rate, the amplitude and frequency of the heart sounds detected by the use of a stethoscope sound pickup piece placed on the chest or in the esophagus will also allow some estimate of the force of cardiac contraction. A stethoscope and associated sound pickup piece is also used to detect and transmit the low frequency and low amplitude sounds associated with conventional "indirect" systolic and diastolic blood pressure determinations. Thus, the stethoscope has become an important diagnostic tool and has gained importance in the course of anesthetic management during both major and minor surgical procedures.
Various electronic stethoscope systems are illustrated in U.S. Pat. Nos. 3,087,016; 3,160,708; 3,790,712; 3,985,121 and 3,989,895. It has also been known to provide electronic apparatus to monitor selected body conditions, develop corresponding electrical signals and broadcast such signals to a receiver unit to be heard by an anesthetist or for transmission to recording apparatus or the like. U.S. Pat. No. 3,552,381 describes an apparatus designed to automatically determine, transmit and display information concerning the patient's physiologic status. No means are provided by which the operator's senses may be used to aid in clinical assessment of the patient's physiologic response to anesthesia. Other shortcomings in the apparatus of U.S. Pat. No. 3,552,381 are also to be noted in that the electronic detector is required to be in intimate contact with the patient whereas it would be desirable to shield the fragile and expensive microphone sound detector from mechanical stress and damage as with the present invention.
Special note should be taken that medical institutions throughout the world have a very sizable investment in precordial, esophageal and pneumatic blood pressure cuff stethoscope equipment. Such institutions also have a substantial investment in assocaited inflation and pressure gauge apparatus. For example, the already owned inflation apparatus may incorporate expensive mechanical, electronic, automatic or semi-automatic components or combinations of the same. Additionally, substantial investments have been made in medical institutions in pressure gauge equipment which may involve expensive mechanical, electronic or fluidic components. Thus, it would be highly desirable to have a transmitter unit which could be utilized with any of the already owned and often expensive stethoscope equipment and inflation and pressure gauge apparatus. In this regard, it may be noted that none of the apparatus described in the mentioned United States patents are adapted to operate already available stethoscope, inflation and pressure apparatus. Play apparatus, e.g., U.S. Pat. No. 4,155,196 is also noted.
Another deficiency in the prior art is to be noted in the fact that the prior art telemetry apparatus tends to produce artificial rather than natural biological sounds. British Pat. No. 1,008,027 published Oct. 22, 1965, for example, teaches a telemetry system in which the output of the microphone is amplified and manipulated to reproduce artificial and simulated low level biological sounds. However, medical practitioners have little desire or need for monitoring devices which artificially alter their perception of diagnostic information. What is needed is a portable system which allows for remote and faithful reproduction of biological sounds of diagnostic importance and the system, in effect, should be an extension of the operator's own senses. Further, the preferred system should not require the presence of an electronic pickup device in intimate contact with the patient as in the British patent or as in U.S. Pat. No. 3,552,381. Further, it would be desirable to have a portable system of the kind mentioned which allows for the intermittent detection of two biological sound sources, namely, heart and breath sounds as one source and blood pressure related Korotkoff sounds as another source and to accomplish the same automatically dependent upon inflation of a pressure cuff associated with the system. Compare, for example, the complex wired input telemetry of U.S. Pat. No. 3,646,606.
Recognition should also be made of another prior art device described in U.S. Pat. No. 3,517,664 and known as a Ploss automatic switch valve which has been uniquely incorporated in one form of the patient monitoring apparatus of the present invention. The Ploss automatic switch valve represents a commercially available pressure operated switching valve sold by Medical Production Division, Minnesota Mining and Manufacturing company of St. Paul, Minnesota, and is conventionally sold for operation in conjunction with standard blood pressure cuffs and manometers and automatic cuff inflation systems. Such a Ploss valve has five tubular connections to the valve. One connection provides a sound output to the anesthetist's monaural or binaural earpiece. A second connection is used to receive pressure from a manometer or semi-automatic inflator whenever it is desired to inflate the cuff. A third connection receives blood pressure related sounds from a blood pressure acoustic pickup. A fourth connection provides an outlet for pressure going to the blood pressure cuff. The fifth connection provides means for receiving sounds from an acoustic precordial or esophageal stethoscope. While the Ploss valve provides a greatly improved system for monitoring either precordial or esophageal sounds, the anesthetist's mobility is physically restricted. In addition, the discomfort of wearing a binaural and/or specially fitted earpiece, the annoyance of a work area cluttered with tubing (e.g., stethoscopes, intravenous fluid lines, naso-gastric tubes, Foley catheters, et cetera) and the extraneous noises produced and amplified by the stethoscope lines getting tangled up and/or hitting other equipment can approach the point of being almost unbearable. Nevertheless, the Ploss-type valve offers many valuable features useful for remote monitoring. So far as is known, however, the Ploss-type valve has never heretofore been used advantageously in a radio-type monitoring system.
As will be noted from the later detailed description of the invention, advantage is taken of using a sound transmitting tube as a means for mounting and enclosing the antenna. In this regard, it may be noted that U.S. Pat. No. 4,072,822 teaches the practice of embedding an electric wire in a specially constructed sound tube associated with a stethoscope. However, this prior art construction has two noticeable disadvantages. First, a special tube is required to be molded and, secondly, if the embedded wire breaks, the entire tubing structure is rendered useless. Thus, it would be desirable in a stethoscope system to have a construction in which a radio antenna can be both mounted and loosely enclosed within the lumen of a sound tube without incurring either of these disadvantages.
As a final aspect of the prior art, the later detailed description of the invention involves the use of Velcro material as a fastening device for the transmitter unit. This aspect of the invention leads to the observation that the prior art telemetry and electronic stethoscope apparatus appears to have given essentially no attention to the rather important aspect of providing a means for releasably posistioning the transmitter unit near the patient but in a manner which allows the normal operating procedures to go on without interference by the transmitter location. A more specific observation can be made to the effect that the prior art has not heretofore taught or suggested a practical means for releasably securing the transmitter unit to the blood pressure cuff.
With the above brief description and limitations of the prior art in mind, there remains a need to provide a radio frequency transmitter-receiver patient monitoring system which allows the operator to selectively receive either blood pressure related sounds or heartbeat and respiratory related sounds and in a manner compatible with both normal operating procedures and patient care. The providing of such a system thus becomes the object of the present invention. Other objects will appear as the description proceeds.